Loss of anthocyanins and modification of the anthocyanin profiles in grape berries of Malbec and Bonarda grown under high temperature conditions

Malbec and Bonarda are the two most widely cultivated grape varieties in Argentina, and their derived red wines are recognized worldwide, being their intense color a major quality trait. The temperature during fruit ripening conditions berries color intensity. In the main viticulture region of Malbec and Bonarda a 2-3°C increase in temperature has been predicted for the upcoming years as consequence of the global climate change. In the present study, this predicted temperature raise was simulated under field-crop conditions, and its effect on anthocyanin pigmentation in berries of Malbec and Bonarda was monitored by HPLC analysis throughout the ripening process, in two growing seasons. Additionally, expression levels of regulatory (MYBA1 and MYB4) and structural (UFGT and Vv3AT) anthocyanin genes were monitored in Malbec berry skins. Although cultivar-dependent time-course variation was observed for total anthocyanin content, in general, the berries of both cultivars grown under high temperature (HT) conditions had significantly lower total anthocyanins (∼28-41% reduction), and a higher proportion of acylated anthocyanins, than their respective controls. Expression of MYBA1 and UFGT, but not MYB4, was correlated with anthocyanin pigmentation at half ripening and harvest, whereas overexpression of the acyltransferase gene Vv3AT was associated with higher anthocyanin acylation in HT berries. These results suggest that color development and pigment modifications in Malbec berries under HT are regulated at transcriptional level by MYBA1, UFGT, and Vv3AT genes. These data contribute to the general understanding on the effect of high temperatures on anthocyanin biochemistry and genetic regulation, and may have direct implications in the production of high-quality wines from Malbec and Bonarda.